Process involving cooling in a static atmosphere for high permeability silicon steel comprising copper

ABSTRACT

A process for producing silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (G/Oe) at 10 oersteds, which includes the steps of: preparing a melt of steel consisting essentially of, by weight, up to 0.07% carbon, from 2.60 to 4.0% silicon, from 0.03 to 0.24% manganese, from 0.01 to 0.09% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, up to 0.02% nitrogen, from 0.1 to 0.5% copper, from 0.00045 to 0.0035% boron, balance iron; casting the steel; hot rolling the steel; annealing the steel prior to a final cold roll at a temperature of from 1400* to 2150*F; cooling the steel from a temperature below 1700*F and above 750*F to a temperature at least as low as 500*F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to the temperature below 1700*F and above 750*F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel; and cold rolling the steel at a reduction of at least 80%.

United States Patent 11 1 Salsgiver et al.

[ 1 Dec. 30, 1975 [75] Inventors: James A. Salsgiver, Sarver; Frank A.

Malagari, Freeport, both of Pa.

[73] Assignee: Allegheny Ludlum Industries, Inc.,

Pittsburgh, Pa.

221 Filed: Nov. 18, 1974 21 Appl. No.1 524,846

3,855,019 12 1974 Salsgiver et a1 11.. 148/112 3,855,020 12/1974 Salsgiver et al 148/112 3,855,021 12 1974 Salsgiveret al 148/112 OTHER PUBLICATIONS Saito, A; Effect of Minor Elements in Silicon Steel, in Nippon Kinzok, Vol. 27, 1963 pp. 191-195. Kussmann, A; Gekupferter Stahl Fur Transform, in

Stahl and Eisen; 1930; pp. 1194-1197.

Primary ExaminerWalter R. Satterfield Attorney, Agent, or Firm-Vincent G. Gioia; Robert F. Dropkin [57] ABSTRACT A process for producing silicon steel having a cubeon-edge orientation and a permeability of at least 1850 (G/Oe) at 10 oersteds, which includes the steps of: preparing a melt of steel consisting essentially of,

by weight, up to 0.07% carbon, from 2.60 to 4.0% silicon, from 0.03 to 0.24% manganese, from 0.01 to 0.09% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, up to 0.02% nitrogen, from 0.1 to 0.5% copper, from 0.00045 to 0.0035% boron, balance iron; casting the steel; hot rolling the steel; annealing the steel prior to a final cold roll at a temperature of from 1400 to 2150F; cooling the steel from a temperature below 1700F and above 750F to a temperature at least as low as 500F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to the temperature below 1700F and above 750F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel; and cold rolling the steel at a reduction of at least 80%.

16 Claims, N0 Drawings PROCESS INVOLVING COOLING IN A STATIC ATMOSPHERE FOR HIGH PERMEABILITY SILICON STEEL COMPRISING COPPER The present invention relates to a process for producing electromagnetic silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (G/O at oersteds.

Oriented silicon steels containing 2.60 to 4.0% silicon are generally produced by processes which involve hot rolling, a double cold reduction, an anneal before each cold roll and a high temperature texture anneal. Characterizing these steels are permeabilities at 10 oersteds of from about 1790 to 1840 (G/O In recent years a number of patents have disclosed methods for producing silicon steels with permeabilities in excess of 1850 (G/O at 10 oersteds. Of these U.S. Pat. Nos. 3,287,183, 3,632,456 and 3,636,579 appear to be the most interesting. A still more interest ing method is, however, described in a copending United States patent application. The application is No. 357,974, and was filed on May 7, 1973 in the names of James A. Salsgiver and Frank A. Malagari. Application Ser. No. 357,974 describes a process which includes the steps of: preparing a melt of steel consisting essentially of, by weight, up to 0.07% carbon, from 2.6 to 4.0% silicon, from 0.03 to 0.24% manganese, from 0.01 to 0.07% sulfur, from 0.015 to 0.04% aluminum, up to 0.02% nitrogen, from 0.1 to 0.5% copper, balance iron; casting the steel; hot rolling the steel; annealing the steel prior to a final cold roll at a temperature of from l400 to 2150F; cooling the steel from a temperature below 1700F and above 750F to a temperature at least as low as 500F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to the temperature below 1700F and above 750F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel; and cold rolling the steel at a reduction of at least 80%.

Described herein is another, and improved method for producing silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (6/0,) at 10 oersteds. It is primarily based upon the discovery that the melts of application Ser. No. 357,974 and another application filed concurrently herewith, can be prepared with boron added thereto. Boron has been successfully used to help develop high permeability in grain oriented silicon steels. The concurrently filed application is US. Ser. No. 524,831. It is primarily.

based upon the discovery that the melt of application Ser. No. 357,974 can be prepared with selenium replacing part or all of the sulfur contained therein.

It is accordingly an object of the present invention to provide a process for producing electromagnetic silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (G/O at 10 oersteds.

The present invention provides a method for producing silicon steel havinga cube-on-edge orientation and a permeability of at least 1850 (G/O at 10 oersteds. Involved therein are the steps of: preparing a melt of silicon steel consisting essentially of, by weight, up to 0.07% carbon, from 2.60 to 4.0% silicon, from 0.03% to 0.24% manganese, from 0.01 to 0.09% of material from the group consisting of sulfur and selenium, from 2 0.015 to 0.04% aluminum, up to 0.02% nitrogen, from 0.1 to 0.5% copper, from 0.00045 to 0.0035% boron, balance iron; casting the steel; hot rolling the steel into a hot rolled band; subjecting the steel to at least one cold rolling; subjecting the steel to a final annealing prior to the final cold rolling; decarburizing the steel; and final texture annealing the steel. Also included, and significantly so, are the specific steps of: carrying out the final anneal prior to the final cold rolling at a temperature of from 1400 to 2150F for a period of from 15 seconds to 2 hours; cooling the steel from a temperature below 1700F and above 750F to a temperature at least as low as 500F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to the temperature below 1700F and above 750F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel; and cold rolling the cooled steel at a reduction of at least 80%. Preferred conditions include annealing at a temperature of from l800 to 2125F,

' cooling with a liquid quenching medium or gaseous stream from a temperature below 1600F and above 1000F, andcold rolling at a reduction of at least Melting, casting, hot rolling, cold rolling, decarburizing and final texture annealing do not involve any novel procedure, as far as techniques are concerned, and with regard to them, the invention encompasses all applicable steelmaking procedures. As to the cold rolling, it should however, be pointed out that several roll passes can constitute a single cold rolling operation, and that plural cold rolling operations exist only when cold rolling passes are separated by an anneal.

In addition to boron, the steel melt must include silicon, aluminum, manganese, and sulfur and/or selenium. Silicon is necessary as it increases the steels resistivity, decreases its magnetostriction, decreases its magnetocrystalline anisotropy and hence decreases its core loss. Aluminum, manganese, and sulfur and/or selenium are necessary as they form inhibitors which are essential for controlling the steels orientation and "its properties which are dependent thereon. More specifically, aluminum combines with nitrogen in the steel or from the atmosphere, to form aluminum nitride; and manganese combines with sulfur and/or selenium, and possibly copper, to form manganese sulfide and/or manganese copper sulfide, and/or manganese selenide and/or manganese copper selenide. All together, these compounds inhibit normal grain growth during the final texture anneal, while at the same time aiding in the development of secondary recrystallized grains having the desired cube-on-edge orientation. Copper, noted above for its presence in manganese inhibitors, can also be beneficial during processing. It is hypothesized that copper can lower the annealing temperature, lower the temperature from which the rapid cool can occur, improve rollability, simplify melting, and relax annealing atmosphere requirements. Moreover, copper increases the steels resistivity and decreases its core loss.

A steel in which the process of the present invention is particularly adaptable to consists essentially of, by weight, from 0.02 to 0.07% carbon, from 2.65 to 3.25% silicon, from 0.05 to 0.20% manganese, from 0.02 to 0.07% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, from 0.0030 to 0.0090% nitrogen, from 0.1 to 0.4% copper,

from 0.0005 to 0.0025% boron, balance iron. This steel has its chemistry balanced so as to produce a highly beneficial structure when processed according to the present invention. As a general rule boron contents will be in excess of 0.0007%.

Although we are not sure why the final anneal prior to thefinal cold rolling, and the controlled cooling of the present invention is so beneficial, we hypothesize: that the anneal conditions the steel for cold rolling and provides an operation during which inhibitors can form; and that the slow cool to a temperature below 1700F and/or the use of annealing temperatures in the lower part of the annealing temperature range, increase the uniformity in which the inhibitors are distributed, as essentially only ferrite phase is present in the steel at temperatures below 1700F, contrasted to the presence of austenite and ferrite phases and different solubilities for the inhibiting elements in each phase at somewhat higher temperatures. As discussed above, the primary inhibitors are aluminum nitride, and compounds of manganese sulfide and manganese selenide. N criticality is placed upon the particular annealing atmosphere. Illustrative atmospheres therefore include nitrogen; reducing gases such as hydrogen; inert gases such as argon; air; and mixtures thereof.

The following examples are illustrative of several aspects of the invention.

Four heats of steel were cast and processed into siliconsteel having a cube-on-edge orientation. The

rolling; subjecting said steel to a final annealing prior to the final cold rolling; decarburizing said steel; and final texture annealing said steel; the improvement comprising the steps of carrying out said final anneal prior to the final cold rolling at a temperature of from 1400 to 2l50F for a period of from 15 seconds to 2 hours; cooling said steel from a temperature below 1700F and above 750F to a temperature at least as low as 500F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to said temperature below 1700F and above 750F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel; and cold rolling the cooled steel at a reduction of at least 80%; said melt consisting essentially, of, by weight, up to 0.07% carbon, from 2.60 to 4.0% silicon, from 0.03 to 0.24% manganese, from 0.01 to 0.09% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, up to 0.02% nitrogen, from 0.1 to 0.5% copper, from 0.00045 to 0.0035% boron, balance 1ron.

2. An improvement according to claim 1, wherein said steel is cooled from a temperature below 1600F and above l0O0F to a temperature at least as low as 500F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature OF and above l 000F at chemistry of the heats appears hereinbelow in Table l. to said temperature below 160 a rate which is no faster than one wherein the steel 8 8 TABLE 1 Composition (wt.

Heat C Mn Si S Al N Cu B Fe A 0.045 0.1 1 2.84 0.035 0.030 0.0078 0.2 0.00048 Bal. B 0.046 0.11 2.85 0.036 0.029 0.0065 0.2 0.00078 Bal. C 0.046 0.11 2.83 0.035 0.030 0.0062 0.19 0.00141 Bal. D 0.1 l 2.84 0.035 0.030 0.0064 0.2 0.00226 Bal.

, approximately 93 mils, heat treating for 1 minute at 2050F, slow cooling to 1740F (approximately seconds), air cooling to l 100F, water quenching from 1 100F, cold rolling to a final gage of approximately 12 mils, decarburizing at a temperature of 1475F in a mixture of wet hydrogen and nitrogen, and final texture annealing at a maximum temperature of 2150F.

The heats were tested for permeability. Respective permeabilities of 1906, 1889, 1873 and 1898 (6/0 at 10 oersteds were recorded. a

It will be apparent to those skilled in the art that the novel principles of the invention disclosed herein in connection with specific examples thereof will suggest various other modifications and applications of the same. It is accordingly desired that in construing the breadth of the appended claims they shall not be limited to the specific examples of the invention described herein.

We claim:

1. In a process for producing electromagnetic silicon steel having a cube-on-edge orientation and a peremeability of at least 1850 (6/0 at 10 oersteds, which process includes the steps of: preparing a melt of silicon steel; casting said steel; hot rolling said steel into a hot rolled band; subjecting said steel to at least one cold tic atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel.

3. An improvement according to claim 1 wherein said final anneal prior to the final cold rolling is at a temperature from 1800 to 2125F.

4. An improvement according to claim 3, where n said steel is cooled from a temperature below 1600 F and above 1000F to a temperature at least as low as 500F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to said temperature below 1600F and above 1000 F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel.

5. An improvement according to claim 1, wherein said steel is cooled to a temperature at least as low as 500F from a temperature below l700F and above 750F with a gaseous stream.

6. An improvement according to claim 1, wherein said steel is cooled to a temperature at least as low as 500F from a temperature below 1700F and above 750F with a liquid quenching medium.

cooled in a sta 7. An improvement according to claim 1, wherein said steel is air cooled to said temperature below l700F and above 750F.

8. An improvement according to claim 3, wherein said steel is cooled to a temperature at least as low as 500F from a temperature below l700F and above 750F with a gaseous stream.

9. An improvement according to claim 3, wherein said steel is cooled to a temperature at least as low as 500F from a temperature below l700F and above 750F with a liquid quenching medium.

10. An improvement according to claim 3, wherein said steel is air cooled to said temperature below l700F and above 750F.

11. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is carried out subsequent to an initial cold rolling.

12. An improvement according to claim 1, wherein said steel consists essentially of, by weight, from 0.02 to 6 0.07% carbon, from 2.65 to 3.25% silicon, from 0.05 to 0.20% manganese, from 0.02 to 0.09% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, from 0.0030 to 0.0090% nitrogen, from 0.1 to 0.4% copper, from 0.0005 to 0.0025% boron, balance iron.

13. An improvement according to claim 12, wherein said steel has at least 0.0007% boron.

14. An improvement according to claim 1, wherein the cooled steel is cold rolled at a reduction of at least 15. An improvement according to claim 3, wherein the cooled steel is cold rolled at a reduction of at least 16. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is applied to a hot rolled band. 

1. IN A PROCESS FOR PRODUCING ELECTROMAGNETIC SILICON STEEL HAVING A CUBE-ON-EDGE ORIENTATION AND A PEREMEABILITY OF AT LEAST 1850 (G OE) AT 10 OERSTEDS, WHICH PROCESS INCLUDES THE STEPS OF: PREPARING A MELT OF SILICON STEEL; CASTING SAID STEEL; HOT ROLLING SAID STEEL INTO A HOT ROLLED BAND; SUBJECTING SAID STEEL TO AT LEAST ONE COLD ROLLING; SUBJECTING SAID STEEL TO A FINAL ANNEALING PRIOR TO THE FINAL COLD ROLLING; DECARBURIZING SAID STEEL; AND FINAL TEXTURE ANNEALING SAID STEEL; THE IMPROVEMENT COMPRISING THE STEPS OF CARRYING OUT SAID FINAL ANNEAL PRIOR TO THE FINAL COLD ROLLING AT A TEMPERATURE OF FROM 1400 TO 2150*F FOR A PERIOD OF FROM 15 SECONDS TO 2 HOURS; COOLING SAID STEEL FROM A TEMPERATURE BELOW 1700*F AND ABOVE 750*F TO A TEMPERATURE AT LEAST AS LOW AS 500*F WITH A LIQUID QUENCHING MEDIUM OR GASEOUS STREAM AND FROM ITS MAXIMUM ANNEALING TEMPERATURE TO SAID TEMPERATURE BELOW 1700*F AND ABOVE 750*F AT A RATE WHICH IS NO FASTER THAN ONE WHEREIN THE STEEL IS COOLED IN A STATIC ATMOSPHERE OR IN A CONTINUOUS PROCESSING LINE WHERE THERE IS SOME RELATIVE MOTION BETWEEN THE ATMOSPHERE AND THE STEEL, ALTHOUGH THE ONLY DELIBERATEMOTION IS THAT IMPARTED TO THE STEEL, AND SAID COOLING THE COOLED STEEL AT A REDUCTION OF ATLEAST 80%; SAID MELT CONSISTING ESSENTIALLY OF, BY WEIGHT, UP TO 0.07% CARBON, FROM 2.60 RO4.0% SILICON, FROM 0.03 TO 0.24% MANGANESE, FROM 0.01 TO 0.09% OF MATERIAL FROMTHE GROUP CONSISTING OFSULFUR ANDSELENIUM, FROM 0.015 TO0.04% ALUMINUM, UP TO 0.02% NITROGEN, FROM 0.1 TO 0.5% COPPER, FROM 0...45 TO 0.00035% BORON, BALANCE IRON.
 2. An improvement according to claim 1, wherein said steel is cooled from a temperature below 1600*F and above 1000*F to a temperature at least as low as 500*F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to said temperature below 1600*F and above 1000*F at a rate which is no faster than one wherein the steel is is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel.
 3. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is at a temperature from 1800* to 2125*F.
 4. An improvement according to claim 3, wherein said steel is cOoled from a temperature below 1600*F and above 1000*F to a temperature at least as low as 500*F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to said temperature below 1600*F and above 1000*F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel.
 5. An improvement according to claim 1, wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700*F and above 750*F with a gaseous stream.
 6. An improvement according to claim 1, wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700*F and above 750*F with a liquid quenching medium.
 7. An improvement according to claim 1, wherein said steel is air cooled to said temperature below 1700*F and above 750*F.
 8. An improvement according to claim 3, wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700*F and above 750*F with a gaseous stream.
 9. An improvement according to claim 3, wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700*F and above 750*F with a liquid quenching medium.
 10. An improvement according to claim 3, wherein said steel is air cooled to said temperature below 1700*F and above 750*F.
 11. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is carried out subsequent to an initial cold rolling.
 12. An improvement according to claim 1, wherein said steel consists essentially of, by weight, from 0.02 to 0.07% carbon, from 2.65 to 3.25% silicon, from 0.05 to 0.20% manganese, from 0.02 to 0.09% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, from 0.0030 to 0.0090% nitrogen, from 0.1 to 0.4% copper, from 0.0005 to 0.0025% boron, balance iron.
 13. An improvement according to claim 12, wherein said steel has at least 0.0007% boron.
 14. An improvement according to claim 1, wherein the cooled steel is cold rolled at a reduction of at least 85%.
 15. An improvement according to claim 3, wherein the cooled steel is cold rolled at a reduction of at least 85%.
 16. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is applied to a hot rolled band. 